Sticking mainly with stuff in the current canon (which I admit, it a bit of a hazy term), how widely do you think it was known that the Palpatine was a force practitioner? Further, how widely was it know that he was AKA Darth Sidious?
In original ANH release, it doesn't seem the Emperor was supposed to be a force adept at all. Later canon revised that, but still in canon was the ANH suggestion that the upper Imperial officer corps regarded Darth Vader as the last of his kind.
Your opinion?